This invention relates to a multipot type disk brake having a plurality of pistons to press at least one of a pair of opposed friction pads.
Multipot type disk brakes are disclosed e.g. in unexamined Japanese patent publications 5-293626 and 9-177843. Such brakes have a brake fluid supply passage defined by a pipe casted in the caliper.
Such disk brakes have merits that no machining is needed to form the fluid passage, that greater freedom of layout of the fluid passage is obtained (which makes it possible to reduce the resistance to the flow through the passage and thus provide smooth flow of brake fluid), and that it is possible to reduce the wall thickness, weight and size of the caliper by reinforcing the caliper with the pipe.
Multipot type disk brakes include a caliper having a plurality of cylinder bores, and pistons each inserted in the respective cylinder bores for pressing at least one of a pair of opposed friction pads. The other friction pad is pressed i) by an outer claw of the caliper (with floating type disk brake), ii) by a single piston, or iii) by a plurality of pistons (with opposed-piston type disk brakes).
In an arrangement in which the fluid passage in the caliper is defined by a pipe casted in the caliper through which the cylinder bores communicate with each other, if the pipe is provided behind the cylinder bores and brake fluid is supplied to the cylinder bores through holes extending from the pipe to the respective cylinder bores, as disclosed in unexamined Japanese patent publication 5-293626, the thickness from the bottoms of the cylinder bores to the outer surface of the caliper tends to be large, thus unduly increasing the thickness of the caliper. Thus, as an alternative measure, arranging a pipe 3 across the cylinder bores 2 has been proposed.
But in this arrangement, in which the pipe 3 has a short pipe 3a separated from the remaining pipe portion by the cylinder bores 2, the following problems are expected.
If the short pipe 3a is not bonded strongly to the caliper 1 when the former is casted in the latter, or if interfacial peeling occurs between the pipe and the caliper due to a difference in thermal expansion coefficient between the materials of the pipe and the caliper or vibrations during finishing, the pipe 3a may shift longitudinally in the hole 4. In the worst case, the pipe may come out of the hole 4, dropping into the cylinder bore 2 at one or the other side therof.
Even if this happens, brake fluid can be supplied smoothly. But the pipe in the cylinder bore 2 can damage the outer periphery of a piston (5 in FIG. 1), or make it impossible to push back the piston to the original position to replace a friction pad which has worn.
An object of this invention is to prevent shift and dropout of a pipe casted in the caliper in a simple manner.